The structure of the photosynthetic membrane will be investigated with a variety of biochemical, biophysical, and electron optical techniques in an effort to form a low resolution (ca. 25 A) map of the membrane. This will be accomplished by detailed studies using the freeze-etching technique on mutant photosynthetic membranes, after these membranes have been characterized as to biochemical composition and photosynthetic activity. These studies should provide identifications to the wide variety of structures observed within the photosynthetic membrane and at its surface. Other studies using similar techniques of chloroplast membranes in various states of physiological activity, and membranes which have been treated with certain denaturing agents, will supplement these studies, and should help to form a dynamic picture of the membrane which will serve as a useful model for the structure and function of other cellular membranes.